Growth Mechanism of InN Nucleation Layers on Epitaxial Graphene Using Metal Organic Vapor Phase Epitaxy and Radio-Frequency Molecular Beam Epitaxy

This paper presents a growth mechanism and a comparative study of the InN nucleation layers grown on epitaxial graphene (EG) by metal organic vapor phase epitaxy (MOVPE) and radio-frequency molecular beam epitaxy (RF-MBE). Before growing InN nucleation layers, the EG surface was formed on 4 degrees off 6H-SiC substrates (both Si- and C-faces) by thermal annealing in Ar ambient. The MOVPE grown InN nucleation layers show three-dimensional (3D) growth from the very beginning due to lack of nucleation centers and for the long migration length on the EG surface. The MOVPE InN on the EG formed on Si-face SiC is nucleated with the step edge, while it is nucleated randomly over the entire EG surface on C-face SiC. In contrast, the RF-MBE InN nucleation layers grown on EG formed on Si-face SiC show a two-dimensional growth mode up to 3 ML, and then a further increase of nucleation layer changes the growth mode to 3D mode. The formation of adsorption sites on the graphene surface by introduction of defects plays a significant role to enhance the nucleation center and grow high-quality layers. A model of the InN nucleation layer on EG is geometrically developed for both growth methods.